Google Software Engineer Internship interview questions

I had two 45 minutes interviews on Hangouts. They started with some questions about my background, like the project I am most proud of or what I am currently seeking besides university. Then they gave me a problem, an example and we talked throughout it.

had an OA - hackerrank of 3 questions. First one was easy. The second one was the hardest. My friend got the same question as me. Pretty sure you should use hash table for the last one.